Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $146.51   4.620%   $153.2788   $153.28   $153.30   $153.30  
  Purchase #2 $108.88   7.147%   $116.6617   $116.66   $116.65   $116.70  
  Purchase #3 $184.50   4.808%   $193.3708   $193.37   $193.35   $193.40  
  Purchase #4 $211.63   10.629%   $234.1242   $234.12   $234.10   $234.10  
  Purchase #5 $67.96   10.168%   $74.8702   $74.87   $74.85   $74.90  
  Purchase #6 $208.93   3.112%   $215.4319   $215.43   $215.45   $215.40  
  Purchase #7 $101.60   3.778%   $105.4384   $105.44   $105.45   $105.40  
  7 purchase totals = $1,030.01       $1,093.1760   $1,093.17   $1,093.15   $1,093.20